Table 1 Summary of parameters, formulae and their description using data extracted from chlorophyll a fluorescence (OJIP) transient.

Extracted parameters

F_t

Fluorescence intensity at time t after onset of actinic illumination

F_{50 μs}or F_{20 μs}

Minimum reliable recorded fluorescence at 50 μs with the PEA- or 20 μs with Handy-PEA-fluorimeter

F_{100 μs} and F_{300 μs}

Fluorescence intensity at 100 and 300 μs, respectively

F_J and F_I

Fluorescence intensity at the J-step (2 ms) and the I-step (30 ms), respectively

F_P (= F_m)

Maximum recorded (= maximum possible) fluorescence at P-step

Area

Total complementary area between fluorescence induction curve and F = F_m

Derived parameters

Selected OJIP parameters

F_o ≅ F_{50 μs}or F_o ≅ F_{20 μs}

Minimum fluorescence, when all PSII RCs are open

F_m = F_P

Maximum fluorescence, when all PSII RCs are closed

V_J = (F_{2 ms} - F_o)/(F_m - F_o)

Relative variable fluorescence at the J-step (2 ms)

V_I = (F_{30 ms} - F_o)/(F_m - F_o)

Relative variable fluorescence at the I-step (30 ms)

M_o = 4 (F_{300 μs} - F_o)/(F_m - F_o)

Approximated initial slope (in ms^-1) of the fluorescence transient V = f(t)

V_K = (F_{300 μs} - F_o)/(F_m - F_o)

Relative variable fluorescence at 300 μs

S_m = EC_o/RC = Area/(F_m - F_o)

Normalized total complementary area above the OJIP (reflecting multiple-turnover Q_A reduction events) or total electron carriers per RC

Fraction of OEC = [1 - (V_K/V_J)]_{treated sample}/[1 - (V_K/V_J)]_control

The fraction of oxygen evolving centers (OEC) in comparison with control

Yields or flux ratios

φ_Po = TR_o/ABS = 1 - F_o/F_m = F_v/F_m

Maximum quantum yield of primary photochemistry at t = 0

ψ_Eo = ET_o/TR_o = 1 - V_J

Probability (at time 0) that a trapped exciton moves an electron into the electron transport chain beyond Q_A^-

φ_Do = DI_o/ABS = 1 - φ_Po = F_o/F_m

Quantum yield at t = 0 for energy dissipation

δ_Ro = RE_o/ET_o = (1 - V_I)/(1 - V_J)

Efficiency with which an electron can move from the reduced intersystem electron acceptors to the PSI end electron acceptors

φ_Ro = RE_o/ABS = φ_Po × ψ_Eo × δ_Ro

Quantum yield for the reduction of end acceptors of PSI per photon absorbed

Specific fluxes or activities expressed per reaction center (RC)

ABS/RC = M_o × (1/V_J) × (1/φ_Po)

Absorption flux per RC

TR_o/RC = M_o/V_J

Trapped energy flux per RC at t = 0

ET_o/RC = (M_o/V_J) × ψ_Eo = (M_o/V_J) × (1 - V_J)

Electron transport flux per RC at t = 0

DI_o/RC = ABS/RC - TR_o/RC

Dissipated energy flux per RC at t = 0

RE_o/RC = (RE_o/ET_o) × (ET_o/RC)

Reduction of end acceptors at PSI electron acceptor side per RC at t = 0

Phenomenological fluxes or activities expressed per excited cross section (CS)

DI_o/CS_o = ABS/CS_o - TR_o/CS_o

Dissipated energy flux per CS at t = 0

Performance index

PI_tot,abs = (RC/ABS) × (φ_Po/(1 - φ_Po)) × (ψ_Eo/(1 - ψ_Eo)) × (δ_Ro/(1 - δ_Ro))

Total performance index, measuring the performance up to the PSI end electron acceptors